JP2949293B2 - Power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electric power steering device (power steering) that assists a force required for steering operation by a rotational force of a motor.
About.

(Prior art)

The steering torque applied to the steering wheel is detected by a torque sensor, and when the detected torque exceeds a predetermined dead zone,
A driving current proportional to the detected torque is passed to a motor for assisting steering to drive the motor, and a steering assist control for assisting a force required for steering of the vehicle by a rotational force of the motor is performed, thereby providing a comfortable driver. 2. Description of the Related Art Electric power steering devices that provide a comfortable steering feeling have been developed.

In such a power steering apparatus, in addition to the above-described steering assist control, a steering angle of a steering mechanism is detected, and when a steering wheel is returned, a return control for controlling a motor with a current corresponding to the steering angle, a temporal control of the steering angle. Various controls such as damping control that reduces the drive current according to the rotational angular velocity of the steering wheel obtained by the change and suppresses the sense of wandering of the steering sensation and dynamic friction control that applies a pseudo-dynamic friction force according to the vehicle speed during steering of the steering wheel are performed. Therefore, a good steering feeling can be obtained.

[Problems to be solved by the invention]

However, in any control, since the motor control is performed by processing according to one type of predetermined control characteristic, the steering feeling of the steering wheel is fixed.

Therefore, it is not possible to obtain a steering sensation that meets the driver's requirements.For example, changes in the control characteristics of the steering assist force due to gender differences between men and women, driving conditions such as urban driving and mountain driving, and wet roads, paved roads, It was not possible to change the steering sensation depending on the road surface conditions such as pavement.

The present invention has been made in view of such circumstances, and by preparing a plurality of characteristic data in various controls and selecting them, a steering feeling according to a driver's preference, a road surface condition, a running state, and the like is obtained. It is an object of the present invention to provide a power steering device capable of performing the following.

[Means for solving the problem]

The power steering apparatus according to claim 1, further comprising a steering assist motor that is controlled by a drive current corresponding to output data from a plurality of sensors including a torque sensor that detects a steering torque applied to the steering wheel. In the taking device, storage means for storing a plurality of control data having a plurality of types of characteristics determined by the relationship between the output data of each sensor and the value related to the drive current, among the plurality of control data,
A selection unit that can select at least one of a damping characteristic, a dynamic friction characteristic, and a return characteristic and an assist characteristic in combination, the selection unit preliminarily stores a plurality of types of characteristics of a plurality of control data. The steering feeling set in combination is arbitrarily selected and changed.

A power steering apparatus according to a second aspect is characterized in that the operation feeling is switched based on detection values of a road surface condition and a traveling state.

[Action]

In the present invention, a plurality of control data having a plurality of types of characteristics determined by a relationship between output data of each sensor and a value related to the drive current are stored in the storage unit, and a plurality of types of control data are stored in the storage unit. Can be arbitrarily selected, and an optimum steering sensation can be obtained according to the driver's preference, road surface condition, detected value of the running state, and the like.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to the drawings showing the examples. FIG. 1 is a partially cutaway front view of a power steering apparatus according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, and FIG. III-III
It is an expanded sectional view by a line.

In the figure, reference numeral 1 denotes a rack shaft, which is fixedly mounted on a part of the vehicle body with its longitudinal direction being the left-right direction and is coaxially inserted into a cylindrical rack shaft case 2. Reference numeral 3 denotes a pinion shaft, which is rotatably supported inside a pinion shaft case 4 provided near one end of the rack shaft case 2 so that its axis is oblique to the rack shaft 1.

As shown in FIG. 2, the pinion shaft 3 is composed of an upper shaft 3a and a lower shaft 3b coaxially connected via a torsion bar 5, and the upper shaft 3a is inserted into the pinion shaft case 4 by a ball bearing 40. It is supported, and its upper end is operatively connected to the steering wheel via a universal joint (not shown). The lower shaft 3b is
With the lower part protruding from the lower opening of the pinion shaft case 4 by an appropriate length, a position near the upper end is supported in the pinion shaft case 4 by a four-point contact ball bearing 41. The four-point contact ball bearing 41 is externally fitted to the lower shaft 3b from the lower end side thereof, and is fitted to the step formed near the upper end of the lower shaft 3b, and externally fitted to the lower end side to be caulked to the outer peripheral surface. The inner side of the inner ring is clamped by the collar 42 and positioned outside the lower shaft 3b in the axial direction. Then, the lower ring 3b and the lower shaft 3b are fitted into the pinion shaft case 4 through the lower opening. An annular shoulder formed at a lower portion of the case 4 and a lock nut 43 screwed into the case 4 from the opening portion sandwiches both sides of the outer ring so as to extend inside the pinion shaft case 4 in the axial direction. It is positioned and applies a radial load acting on the lower shaft 3b and an axial load in both directions.

In the middle of the lower shaft 3b protruding from the pinion shaft case 4, pinion teeth 30 extending over an appropriate length in the axial direction are provided.
When the pinion shaft case 4 is fixed to the upper side of the rack shaft case 2 by a fixing bolt 44, the pinion teeth 30 are provided inside the rack shaft case 2 at one end of the rack shaft 1. The rack teeth 10 mesh with the rack teeth 10 formed at an appropriate position in the axial direction at the position near the part, and the lower shaft 3b and the rack shaft 1 are engaged with each other while the axes thereof are obliquely crossed. The lower shaft 3b extends further downward than the position of engagement with the rack shaft 1, and its lower end is coaxial with the lower shaft 3b, and the large bevel gear 31 is fitted with its tooth forming surface facing downward. The bevel gear 31 is supported by a needle roller bearing 33 in a bevel gear housing 20 continuously provided below the rack shaft case 2 so as to surround the large bevel gear 31. Therefore, the lower shaft 3b is formed by the four-point contact ball bearing 1 and the needle roller bearing 33 by the rack teeth.
It is supported on both sides of the meshing position between the pinion 10 and the pinion teeth 30, and the amount of bending generated on the lower shaft 3b at the meshing position is kept within a predetermined allowable range.

Further, at a meshing position between the rack teeth 10 and the pinion teeth 30, a rack guide 12 for pressing the rack shaft 1 by the urging force of the pressing spring 11 toward the pinion shaft 3 is provided so that the rack teeth 10 and the pinion teeth 30 are meshed without any gap. The rack shaft 1 is supported by the rack guide 12 and the lower shaft 3b sandwiched from both sides in the radial direction at the meshing position, and the rack shaft case on the opposite side to the position where the rack shaft 12 is connected to the pinion shaft case 4 is opposite. 2 is supported by a bearing bush 13 fitted inside the end of the rack shaft case 2, and is movable in the axial direction inside the rack shaft case 2. The left and right ends of the rack shaft 1 protruding from both sides of the rack shaft case 2 are respectively connected via separate ball joints 14,
The tie rods 15 are connected to left and right wheels (not shown), respectively, and the wheels are steered left and right by moving the rack shaft 1 in the axial direction.

Reference numeral 6 in FIG. 2 denotes a torque sensor for detecting a steering torque applied to the steering wheel. The torque sensor 6 is externally fitted to the upper shaft 3a, rotates together with the upper shaft 3a, and has a lower end face centered on the axis of the upper shaft 3a. A resistor holding member 60 having an annular resistor formed therein, and a detector which is fitted on the lower shaft 3b, rotates together with the lower shaft 3b, and slidably contacts an upper end surface of the resistor with a radial point on the resistor. The detector holding member 61 thus formed constitutes a potentiometer. The upper shaft 3a of the pinion shaft 3 rotates around its axis in accordance with the rotation of the steering wheel, while the lower shaft 3b receives a road surface resistance acting on the wheels via the rack shaft 1, and the two shafts The torsion bar 5 interposed therebetween is twisted according to the steering torque applied to the steering wheel. The torque sensor 6 includes an upper shaft 3a and a lower shaft according to the torsion of the torsion bar 5.
3b is output as a potential corresponding to a sliding contact position between the detector and the resistor. When the torsion bar 5 is not twisted, in other words, when the steering wheel is operated, The initial adjustment is performed so that a predetermined reference potential is output when the operation is not performed. Torque sensor 6
Are output to the control unit 7 in time series, and the control unit 7 compares this signal with the reference potential to recognize the direction and magnitude of the steering torque, and is arranged as described later. A drive signal is issued to the steering assist motor 8.

The steering assist motor 8 transmits the rotational force to the lower shaft 3b via the electromagnetic clutch 16, the planetary gear reducer 9, and the smaller bevel gear 32 having a smaller diameter meshing with the larger bevel gear 31. It is.

The electromagnetic clutch 16 has an annular shape, and includes a coil portion 161 fixed to an intermediate case 81 of the motor 8 and a rotating shaft 80 of the motor 8.
The main driving portion 162 is coaxially fitted on one side of the outer peripheral portion and rotates with the rotary shaft 80. The main driving portion 162 has a disk shape and faces the main driving portion 162. Part 1
The motor 8 is constituted by an engaging and disengaging portion 163 for engaging and disengaging the rotational force of the motor 8.

The planetary gear reduction device 9 is internally fitted in the engagement / disengagement portion 163, rotates and has a sun gear, one end of which is supported by a bearing internally fitted in the main driving portion, and the other end of which is internally fitted in a planet carrier 93 described later. A sun shaft 90 supported by the mounted bearing, an annular outer ring 91 fixed to the casing end surface 82 of the motor 8 coaxially with the rotating shaft 80, an inner peripheral surface of the outer ring 91 and the outer ring 91. Sun axis
A plurality of planetary gears 92, 92, which are respectively in contact with the outer peripheral surface of the sun gear 90, rotate around respective axes, and revolve around the axis of the sun gear, and these planetary gears 92, 92 ... The motor 8 and the electromagnetic clutch 16 are integrally formed on one side of a rotary shaft 80 with a smaller outer diameter than the motor 8. The output shaft 94 of the planetary gear reduction device 9 is fitted and fixed at the axial center position of the planet carrier 93 located coaxially with the rotation shaft 80 of the motor 8, and protrudes from the casing by an appropriate length. The small bevel gear 32 is fitted to the distal end of the output shaft 94 with its tooth forming surface facing the distal end side. The small bevel gear 32 is mounted together with the output shaft 94 on the planetary gears 92, 92,. It rotates according to the revolution of.

The motor 8, the electromagnetic clutch 16 and the planetary gear reducer 9
In the state where these axes are substantially parallel to the axis of the rack shaft 1, the small bevel gear 32 is fitted inside the bevel gear housing 20, and the small bevel gear is 32 is a large bevel gear fitted to the lower end of the lower shaft 3b
It is engaged with a bracket 2a provided outside the rack shaft case 2. The backlash adjustment between the large bevel gear 31 and the small bevel gear 32 is performed when the planetary gear reduction device 9 is fitted inside the bevel gear housing 20 when the casing of the planetary gear reduction device 9 and the bevel gear housing 20 abut. It can be easily performed by changing the thickness and / or the number of the shims to be interposed in the vehicle.

On the other side of the rotation shaft 80 of the motor 8, there is provided a rotation detector 17 for detecting the rotation position of the motor 8.
Is a disk-like shape fitted externally to the other side of the rotating shaft 80 of the motor 8, has a magnet plate 170 having two N poles and two S poles, and a predetermined mounting angle β (in this embodiment, β = 135 °) and two mounted reed switches 171,171. FIG. 4 is a waveform diagram showing an output waveform of the rotation detector. Since the two reed switches 171 and 171 are mounted without the mounting angle β of 135 °, the output waveforms are output 90 degrees out of phase. Since four waveforms are output in each rotation, the rotation detector 17 has a resolution of 1/16 of one rotation by detecting its rising and falling.

The rotation detector 17 can detect the rotation speed from 0 and can detect the relative position of the rotor, as compared with a conventional rotation detector such as a tacho generator.

In addition, it is smaller than a photointerrupter type rotary encoder, resistant to high temperatures, has less aging, and is less expensive. Further, since the output waveform is a pulse output, the detection result can be easily taken into a CPU such as a microcomputer.

FIG. 5 is a block diagram showing the configuration of the control unit 7. The control unit 7 includes, in addition to the output signal of the torque sensor 6, the output signal of the rotation detector 17 and the vehicle speed detector 18 for detecting the vehicle speed. The output signal and the switching result of the characteristic switching unit 19 having eight switches S1 and S2 to S8 for switching the steering feeling and the switching result of the ignition key 51 for opening and closing the power supplied by the power supply 50 are input. Done, motor 8
And a drive signal for driving the clutch 16 is output.
Here, the switches S1 to S8 are any one of the switches S1 to S8.
Is turned off automatically when is turned on,
One of the switches S1 to S8 is turned on among the steering feelings described later.

The control unit 7 outputs an output signal or a switching result from the torque sensor 6, the rotation detector 17, the vehicle speed detector 18, and the characteristic switching unit 19.
An interface 76 for converting the data into a form that can be taken into the microcomputer 70 by processing such as A / D conversion, a power supply circuit 77 for generating various powers to be supplied to the microcomputer 70 from the power supplied from the power supply 50, and a steering assist Microcomputer 70 that performs control for generating a PWM signal by PID control based on an output signal from the microcomputer 70 and outputs a motor drive current, and a clutch that disengages and disengages the clutch when an abnormality occurs. The clutch drive circuit 78 outputs a drive signal.

The microcomputer 70 is a CP for performing various arithmetic processing.
It has a memory unit 702 for storing U 701 and various control programs, various tables and data described later.

 Next, control by the control unit 7 will be described.

FIG. 6 is a block diagram showing a functional configuration and a control operation of a main part of the control unit.

The torque detection signal of the torque sensor 6 is given to a phase compensator 71a for advancing the phase and stabilizing the system, and to a midpoint calculator 71b for calculating a midpoint of the steering angle. The torque detection signal given to 71a is phase-compensated there, and given to the subtractor 74a as a compensation detection torque Tc.

The vehicle speed detection signal of the vehicle speed detector 18 includes an instruction current function unit 73a for generating an instruction current I of the motor 8 described later and a subtraction source signal S _r0 for subtracting the torque detection signal and the instruction current I. a subtraction signal function unit 73b to be generated, the subtraction and the dynamic friction signal function unit 73c which generates a dynamic friction signal S _f which is added to the original signal S _r0, the midpoint computing section 71b, return to control the current during return control unit 73d and given respectively. The rotation position signal of the rotation detector 17 is given to a relative steering angle calculation unit 71g and an angular velocity detection unit 71d for calculating a relative steering angle, and the rotation position signal given to the angular velocity detection unit 71d is The differential operation is performed by the unit 71d, and is supplied to the subtraction signal function unit 73b and the dynamic friction signal function unit 73c as the angular velocity ω.

Wherein in the subtraction signal function part 73b, are being function of stored angular velocity ω and the subtraction original signal S _r0 3 different kinds relationship of gain and damping table DT1, DT2, DT3 according to the value of the vehicle speed V, the In the damping tables DT1, DT2, and DT3, a subtraction source signal _Sr0 having a smaller gain is obtained in this order, and the damping table DT2 shows normal damping characteristics. Then, in the subtraction signal function unit 73b, a subtraction source signal S _r0 is obtained from the angular velocity ω and the vehicle speed V, and the subtraction source signal S
_r0 is provided to the adder 74d.

FIG. 7 shows a damping table D in the subtraction signal function part 73b.
4 is a graph showing a relationship between T2 and the angular velocity ω of the subtraction source signal _Sr0 , in which the vertical axis represents the subtraction source signal _Sr0 and the horizontal axis represents the angular velocity ω. As shown in FIG. 7, the subtraction source signal S _r0 increases in proportion to the increase of the angular velocity ω, and the proportional relation is expressed by the vehicle speeds V ₁ and V
₂ , V ₃ (where V ₁ <V ₂ <V ₃ ), and as the vehicle speed V increases, the ratio (gain) of the subtraction source signal S _r0 to the input angular velocity ω increases. I have. For this reason,
The subtraction source signal _Sr0 increases as the vehicle speed V and the rotational angular speed ω increase. Further, the dynamic friction signal function unit 73c
In the above, the angular velocity ω and the dynamic friction signal S _f are determined according to the value of the vehicle speed V.
Friction tables MT1, MT2, MT3 with different gains
To be a function of is stored, the dynamic friction signal S _f obtained from the angular velocity ω and the vehicle speed V, the animal friction signal S _f is applied to the adder 74d. Dynamic friction table MT1, MT2, MT3 in this order, the gain is small dynamic friction signal S _f is obtained, kinetic friction table MT2 shows a typical dynamic friction characteristics. Figure 8 is a graph showing a characteristic of the relationship between the dynamic friction signal S _f and the angular velocity ω of the dynamic friction table MT2 of dynamic friction signal function unit 73c, taking an angular velocity ω of dynamic friction signal S _f in Tatedo, also the horizontal axis It is. The positive side of the horizontal axis angular velocity ω indicates the angular velocity ω for right steering, and the negative side indicates the angular velocity ω for left steering. The dashed line indicates the above-described characteristic that varies depending on the vehicle speeds V ₁ , V ₂ , and V ₃ (where V ₁ <V ₂ <V ₃ ). The angular velocity ω indicates that the steering wheel was slightly steered.
Detected by, the angular velocity ω is output a constant kinetic friction signal S _f which is determined in advance when it becomes a predetermined value or more. The output value of the dynamic friction signal S _f is assumed to output a large value in accordance ... vehicle speed V _1, V _2, V ₃ increases. This dynamic friction signal S _f is
Because it is output uniformly from minute steering to sharp steering,
It is given as pseudo dynamic friction force for steering of the steering wheel. Particularly during high-speed running has the dynamic friction signal S _f is the steering sense becomes heavy when fine steering of the steering wheel for a large effect, the steering stability is improved.

On the other hand, the rotational position signal given to the relative steering angle calculation unit 71g is processed by a
b and the subtractor 74e, and the steering angle Δθ is calculated from the difference from the midpoint θ _0, and the calculated steering angle Δθ is returned to the return control unit 73d.
Given to.

Return control unit 73d returns three different relationships of gain value steering angle Δθ and the change current I _a in accordance with the vehicle speed V table
The change current _Ia is converted into a function of RT1, RT2, and RT3 and stored, and the change current _Ia is obtained from the steering angle Δθ and the vehicle speed V, and is provided to the instruction current function unit 73a. Here, return tables RT1, RT2, RT3
In this order, _a change current Ia with _a small gain is obtained in this order. The return table RT2 shows normal return characteristics.

Figure 9 is a graph showing the relationship between the change in current I _a and the steering angle Δθ of the return table RT2 in return control unit 73d, a change current I _a to the vertical axis, also taking the steering angle Δθ to the horizontal axis I have. Change current I _a as shown in FIG. 9 increases substantially in proportion to an increase in the steering angle [Delta] [theta], the proportionality vehicle speed _{V 1, V 2, V 3} ( where V ₁ <V ₂ <
Depending on V _3), the vehicle speed V becomes faster, the ratio of change in current I _a for the steering angle Δθ input (gain) is adapted to be small. Therefore, the change current I _a is the vehicle speed V decreases, increases as the steering angle Δθ becomes larger.

In the adder 74d, a dynamic friction signal is added to the input subtraction source signal _Sr0.
S _f is added, the addition result is supplied as a subtraction signal S _r to the first gain compensation unit 75a and the second gain compensation unit 75b. In the first gain compensation unit 75a, subtracts the torque T _r for subtracting either the compensation detected torque T _c by subtraction signal S _r Contact predetermined multiple is inputted is calculated, this calculation result is supplied to the subtracter 74a .

In the subtractor 74a, a subtraction for calculating a subtraction torque _Tr from the input compensation detection torque _Tc is performed, and the result of the subtraction is given to the instruction current function unit 73a as the input torque T.

In the command current function unit 73a, the relationship between the input torque T and the command current I is different depending on the value of the vehicle speed V.
Type of the assist table AT1, AT2, AT3 are functions of has been stored, the input torque T, the vehicle speed V and change current I _a from the command current I is obtained, the command current I is supplied to the subtractor 74b. In the assist tables AT1, AT2, and AT3, a small gain is obtained in this order, and the steering assist force decreases. Here, the assist table AT2 shows normal assist characteristics.

FIG. 10 shows the assist table AT2 in the command current function unit 73a.
Is a graph showing the characteristics of the relationship between the instruction current I and the input torque T, wherein the vertical axis represents the instruction current I and the horizontal axis represents the input torque T. The positive side of the input torque T on the horizontal axis indicates the input torque T for right steering, and the negative side indicates the input torque T for left steering. The positive side of the instruction current I is the motor 8
Shows a current for rotating right steering, and a negative side shows a current for rotating left steering. Further one-dot chain line speed V _1, V _2, V ₃
Shows the instruction current I is changed differently the characteristics and the broken lines by a change current I _a during the return steering wheel defined by the steering angle Δθ and the vehicle speed V at the return control unit 73d by.

Further, -D to D indicate dead zones, and the input torque T of rightward (or left) steering by steering operation is changed to the dead zone.
When the input torque T exceeds the range of D, the command current I of the motor 8 increases as the input torque T increases, and the steering assist force by the motor 8 increases. In this case, the input torque T reaches the low torque setting value -T _s through T _s is independently an instruction current I increases and the vehicle speed V input, the input torque T and the command current I exceeds this relationships vehicle speed _{V 1, V 2, V 3} ( where _{V 1 <V 2 <V 3} )
The command current I with respect to the input torque T decreases as the vehicle speed V increases.

For example, by operating the steering wheel to the right (or left), then to return the該舵wheels, change current -I _a that the input torque T is shown by a broken line if placed in the dead zone -D～D (or I _a) is command current I, and the subsequently when the instruction current I input torque T is within the dead zone -D~D is constant control this change current -I _a (or I _a), the motor 8 is driven at a constant torque. As a result, the steering assist force at the time of returning the steering wheel becomes constant.

This change current being adapted to I speed V absolute value that is input to the return control portion 73d of _a increases as decreases, whereby next to the command current I is larger as the vehicle speed V is decreased, the steering wheel return force I try to make it bigger.

In each of the above tables, the normal state is that of each suffix 2, and the selection is made of eight types of switches corresponding to the steering feeling.
S1~S8 are selected by the selection signal S _s from the characteristic switching section 19 provided with.

Further, in the second gain compensation unit 75b, the subtraction current I _r which is subtracted from the command current I by a predetermined factor a subtraction signal S _r to be inputted is calculated, this calculation result is the subtracter
Given to 74b.

In the subtractor 74b, a subtraction current I _{r is} subtracted from the input instruction current I.
Is subtracted, and the result of the subtraction is provided to the subtractor 74c. In the subtractor 74c, from the result of the subtraction,
A current detection resistor (not shown) is inserted into the motor line to detect current consumption of the motor 8.
Feedback signal is reduced, and the result of the subtraction is
PID calculation processing section 72a for performing PID control and PWM (Pulse Width
Modulation (pulse width modulation) is given to the motor 8 via a drive circuit 72b. The current detection circuit 71c is configured to detect current including the flywheel current of the motor, and the current loop is stabilized.

 Next, the steering control operation will be described.

In this case, the steering sensations are light steering sensation, heavy steering sensation, clean steering sensation, stable steering sensation,
Eight types of steering sensations, such as sporty steering sensation, strong steering sensation in the center, sharp steering sensation and heavy steering sensation, are obtained. These are the characteristic switching units 19 in this order.
Corresponding to the changeover switches S1 to S8, and the changeover switch S1
Select the steering feeling by turning S8 on and off.

FIG. 11 is a flowchart of a main routine showing a process of selecting a steering feeling. Initially, initial setting is performed (step # 1), a vehicle speed V is detected by a vehicle speed detector 18, and the detected speed is stored in a memory unit in the control unit 7. 702 (step # 2). Similarly, in steps # 3 to # 4, the steering angle and angular velocity are detected and stored in the memory unit 702. Next, on / off of the changeover switch is determined in steps # 5 to # 12, and steps # 13 to # 16 and # 17 are determined accordingly.
~ Step # 20, Step # 21 ~ Step # 24, Step # 25 ~ Step # 28, Step # 29 ~ Step # 32,
In each of steps # 33 to # 36, step # 37 to step # 40, step # 41 to step # 44, and step # 45 to step # 48, three characteristics are obtained in order to obtain the steering feeling described above. Assist table AT1,
AT2, AT3, return tables RT1, RT2, RT3, damping tables DT1, DT2, DT3, and dynamic friction tables MT1, MT2, MT3, a combination in which one having one characteristic is selected one by one for the switches S1 to S8. Selection is made by turning on and off, and these are stored in the memory unit 702. Hereinafter, specific combinations will be described.

In the case where a table indicating the normal characteristic of reference numeral 2 is selected at the time of description, the description is omitted.

For example, when a weak driver steers, it is necessary to obtain a light steering feeling. In this case, the switch S1 is turned on, and the assist table AT1 is selected (steps # 13 to # 13).
Step # 16) The rate of increase of the command current I with respect to the torque is made larger than usual.

Conversely, if a heavy steering feel is required, switch S2 is turned on and assist table AT3 is selected (step # 17).
~ Step # 20).

To obtain a clear steering feeling with less friction, turn on the switch S3, select the return table RT1, the damping table DT3, and the dynamic friction table MT3 (steps # 21 to # 24), and change the change current _Ia . In addition to increasing the return force, the damping amount and the dynamic friction force are reduced, and the braking force acting on the steering wheel is reduced.

To obtain a stable steering feeling when driving at high speed, etc., turn on the switch S4, select the assist table AT3, the damping table DT1, and the dynamic friction table MT1 (steps # 25 to # 28), and set the steering assist force. , The steering force is increased, and the braking force is increased as a whole so as to provide a stable steering feeling as a whole.

If you want to feel sporty steering feeling by feeling the reaction force from the road surface like running on mountain road, turn on switch S5, assist table AT3, return table RT1, dynamic friction table MT.
3 (Steps # 29 to # 32) to increase the steering force and increase the assisting force when returning, allowing the steering wheel to be returned quickly, further reducing the dynamic friction force, and reducing the reaction force from the road surface. Is transmitted to the steering wheel.

When it is desired to obtain a strong feeling of steering, such as traveling on an unpaved road, turn on the switch S6, select the return table RT1 and the damping table DT1 (steps # 33 to # 36), and assist in returning. Increase the force and increase the damping force according to the angular velocity.

To obtain a sharp steering feel with excellent turning characteristics, turn on the switch S7, assist table AT1, return table RT1, damping table DT3, dynamic friction table.
Each of the MT3s is selected (step # 37 to step # 40) to provide a light steering feeling as a whole.

Turn on switch S8 if you want to get a solid steering feel that is responsive,
The AT3, the return table RT3, the damping table DT1, and the dynamic friction table MT1 are each selected (Step # 41 to Step # 44), and the steering feeling is generally cheerful.

When none of the switches S1 to S8 is turned on, the gain of each of the characteristics is in a neutral state, and the steering feels normal (steps # 45 to # 48).

In the main routine described above, it is determined whether the switches S1 to S8 are on or off, and the selection of each table is completed.
702 is stored.

Next, an interruption routine using each detected value stored in the main routine and the characteristic data of each table will be described.

FIG. 12 is a flowchart showing an interrupt routine.

First, the steering torque T is detected based on the torque detection signal from the torque sensor 6 (step # 50), and the phase compensation unit 71a
Performs the phase lead calculation (step # 51). Next, the vehicle speed V, the steering angle Δθ, and the angular speed ω stored in the main routine are read from the memory unit 702, respectively (steps # 52 to # 5).
4) Read out each of the four selected tables (step # 5)
Five). Then, a damping amount is set from the damping tables DT1, DT2, DT3 and the dynamic friction tables MT1, MT2, MT3 (step # 56), and a damping torque process is performed by the first gain compensator 75a and the subtractor 74a (step # 57). A steering assist instruction current I is set from the assist tables AT1, AT2, AT3 (step # 58). Return table RT1, RT2, RT
3 return amount handle is set from (step # 59), the assist table AT1 change current I _a based thereon, AT2,3AT
Handle return current processing to be given to the
60). The subtraction current I _r by the subtractor 74b by damping current process is subtracted from the set command current I, the subtraction result is supplied to the subtracter 74c as the current target value of the control.

Then, a PID calculation is performed by the PID calculation processing unit 72a, and a drive signal pulse-width modulated by the PWM drive circuit 72b is output to the motor 8 using the duty ratio obtained from the PID calculation (step #).
63 to step # 64), and return.

In this embodiment, the characteristic selecting means is constituted by a switch, and each characteristic is selected by turning the driver on and off. However, the present invention is not limited to this. For example, road surface conditions, running conditions, etc. Needless to say, it may be automatically detected.

〔effect〕

As described above, in the present invention, among a plurality of control data, at least one of the damping characteristic, the dynamic friction characteristic, and the return characteristic can be selected in combination with the assist characteristic, and the combination is set in advance. Since there is provided a selection means for arbitrarily selecting and changing the steering sensation, an excellent effect that an optimum steering sensation can be obtained according to the driver's preference, road surface condition, running state, and the like is achieved.

[Brief description of the drawings]

1 is a partially cutaway front view showing an embodiment of a power steering apparatus according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a structure of a rotation detector. III-I of FIG.
FIG. 4 is a waveform diagram showing an output waveform of a rotation detector, FIG. 5 is a block diagram showing a configuration of a control unit, and FIG. 6 is a functional configuration and operation of a main part of the control unit. 7 to 10 are graphs showing control characteristics in each function unit, FIG. 11 is a flowchart showing a procedure of a main routine, and FIG. 12 is a flowchart showing a procedure of an interrupt routine. . 6 ... torque sensor, 8 ... motor, 17 ... rotation detector, 18 ... vehicle speed detector, 19 ... characteristic switching section, 73a ... instruction current function section, 73b ... subtraction signal function section, 73c ... ... Dynamic friction signal function part, 73d ... Return control part AT1, AT2, AT3 ... Assist table DT1, DT2, DT3 ... Damping table MT1, MT2, MT3 ... Dynamic friction table RT1, RT2, RT3 ... Return table

Continuation of front page (56) References JP-A-63-71480 JP, A) JP-A-62-295777 (JP, A) JP-A-2-246871 (JP, A) (58) Fields investigated (Int. . ^6, DB name) B62D 5/04

Claims (2)

(57) [Claims] 1. A power steering apparatus comprising: a steering assist motor controlled by a drive current according to output data from a plurality of sensors including a torque sensor for detecting a steering torque applied to a steering wheel; Storage means for storing a plurality of control data each having a plurality of types of characteristics determined by a relationship between output data of the drive current and a value related to the drive current; and a damping characteristic, a dynamic friction characteristic, and a return characteristic among the plurality of control data. Selecting means for selecting at least one of the characteristics and an assist characteristic in combination, wherein the selecting means includes a steering sensation set in advance by combining a plurality of types of characteristics of a plurality of control data. Characterized in that the power steering device is arbitrarily selected and changed. 2. The power steering apparatus according to claim 1, wherein said selection means switches the steering feeling based on detected values of a road surface condition and a running state.